Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 12-25-2007, 01:21 PM   #1
Newbie
 
Join Date: Dec 2007
Posts: 4
Rewards Points: 10
Default

Furnace cycles to often


I have a Comfortmaker RPJ gas unit (around 1984 model) . The unit is cycling every 10-13 mins and it is not that cold out here in Ohio yet ( 30 deg ) . Here is what happens , the stat calls for heat and the draft motor starts to run , the burners light and stay lit for 3-4 mins , just before the burners and draft motor kick off the blower starts to move air through the ducts and shuts off in about 1 minute . The thermostat is a digital unit and I don't think the furnace is putting out enough heat to satisfy the stat causing the frequent cycling . Could it be the limit switch needing adjustment ? . Thank you for any responses .

DRAZOR is offline   Reply With Quote
Old 12-25-2007, 02:06 PM   #2
Union HVAC Tech.
 
Join Date: May 2007
Location: New Jersey
Posts: 607
Rewards Points: 500
Default

Furnace cycles to often


There may be a heater i n the limit that isn't working any longer. You may just want to replace the fan-limit switch if it is original.

bigMikeB is offline   Reply With Quote
Old 12-25-2007, 02:27 PM   #3
Newbie
 
Join Date: Dec 2007
Posts: 4
Rewards Points: 10
Default

Furnace cycles to often


I pulled the cover off and it looks like the settings on the switch are 85-115-160 . Do these sound about right ? . It is more than likely the original switch so I might just go ahead and replace it .
DRAZOR is offline   Reply With Quote
Old 12-26-2007, 07:36 AM   #4
Building and plumbing
 
USP45's Avatar
 
Join Date: Dec 2007
Location: farmville, VA
Posts: 244
Rewards Points: 150
Default

Furnace cycles to often


Sounds to me as if this is the limit switch not working.
First off let me explain what it does so you know why its not working. The lower setting tells the blower fan to shut off so as not to blow cool air into the house. The second or middle temp tells the fan when the combustion chamber is hot enough to start blowing air. The third and highest setting is to shut the entire furnace down. 160 seems a bit low, I usually have it set at 200, BUT it also depends on the manufacturer. DO NOT EVER set the third setting any higher than the original setting because if for some reason the furnace should get stuck and keep running, or the blower does not come on and blow the heat off the combustion chamber then it could burn a hole in it causing a fire. replacing it is very easy. Make sure that the new one is of the same lenth as there are different lenth switches.
USP45 is offline   Reply With Quote
Old 12-26-2007, 11:39 AM   #5
Union HVAC Tech.
 
Join Date: May 2007
Location: New Jersey
Posts: 607
Rewards Points: 500
Default

Furnace cycles to often


140 on, 120 off and 190-200 limit are more normal for that unit.
bigMikeB is offline   Reply With Quote
Old 12-26-2007, 02:15 PM   #6
Newbie
 
Join Date: Dec 2007
Posts: 4
Rewards Points: 10
Default

Furnace cycles to often


Any ideas on who might carry this switch ? .
DRAZOR is offline   Reply With Quote
Old 12-26-2007, 02:55 PM   #7
Union HVAC Tech.
 
Join Date: May 2007
Location: New Jersey
Posts: 607
Rewards Points: 500
Default

Furnace cycles to often


I don't know about your area but suppliers in my area won't sell to home owners.
bigMikeB is offline   Reply With Quote
Old 01-03-2008, 02:14 PM   #8
Newbie
 
Join Date: Dec 2007
Posts: 4
Rewards Points: 10
Default

Furnace cycles to often


I replaced the switch and all is back to normal . Thanks to the above posters for your input and to a great site for getting the info I needed ! .

DRAZOR is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Heil Furnace Burner Problem timothyr HVAC 79 02-12-2014 07:01 PM
Bryant Furnace main burner goes out after 5 seconds Da_Bears HVAC 8 01-03-2012 01:24 AM
Furnace Help tuasoi HVAC 2 11-29-2007 12:54 PM
oil furnace cycles frequently rachs79 HVAC 4 04-18-2007 06:36 PM
Replacing My Furnace, few simple questions compression HVAC 10 02-03-2007 05:00 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.